Injector pumps

ABSTRACT

An injector pump wherein a low-pressure fluid supply duct surrounds a high-pressure fluid supply duct and a ring of nozzles in said high-pressure duct is arranged to discharge radially into a mixing throat formed between two closely spaced radially extending plates or discs, said throat interconnecting with the low-pressure duct such that a fluid issuing from said nozzles would entrain a fluid from the low-pressure duct.

United States Patent Inventor Malcolm Leslie Hoggarth Solihull, England Appl No 796,707 Filed Feb. 5, 1969 Patented June 8, 1971 Assignee The Gas Council London, England Priority Feb. 14,1968 Great Britain 7279/68 INJECTOR PUMPS 1 Claim, 2 Drawing Figs.

U.S.Cl 417/161, 417/163 Int. Cl. F04f 5/00, F04f5/22,F04f5/46 Field 01 Search 230/92, 95,

n 13,ss3,s31

Primary Examiner-Carlton R. Croyle Assistant Examiner-John J. Vrablik Attorney-Larson, Taylor & Hinds ABSTRACT: An injector pump wherein a low-pressure fluid supply duct surrounds a high-pressure fluid supply duct and a ring of nozzles in said high-pressure duct is arranged to discharge radially into a mixing throat formed between two closely spaced radially extending plates or discs, said throat interconnectin'g with the low-pressure duct such that a fluid issuing from said nozzles would entrain a fluid from the low-pressure duct,

INJECTOR PUMPS BACKGROUND OF THE INVENTION This invention relates to injector pumps wherein a jet of gas or liquid from a high-pressure supply is used to entrain another fluid at a lower pressure such'that during the act of entrainment the high-pressure fluid is throttled and the lowpressure fluid compressed, the resultant mixture being discharged at an intermediate pressure between the initial high and low pressures of the fluids.

This form of pump is particularly useful as a booster in compressing a low-pressure gas to a useful working pressure, for example, by entraining a low-pressure gas in a high-pressure gas flow and thereby mixing the two gases it is possible to produce a specific gas mixture at a desired intermediate pressure.

Known forms of gas pressure booster may be of single or multistage construction and in the conventional arrangement a high-pressure supply nozzle, mixture throat and diffuser chamber for each stage are arranged along a common longitudinal axis. Where large gas flows are concerned, the overall longitudinal dimensions of the booster units tend to be considerable even though the cross-sectional areas of the components are relatively small. For example, a single stage booster with a driving gas flow of 500,000 cu.ft./hour has a length approaching 20 feet and a two stage unit may have a total length of 30 feet.

It is therefore an object of the present invention to provide a new and improved form of injector pump suitable for use as a compact gas pressure booster.

SUMMARY OF THE INVENTION According to the invention an injector pump comprises a high-pressure fluid supply duct, a low-pressure fluid supply duct surrounding said high-pressure duct, a circumferential ring of nozzles in said high-pressure duct arranged to discharge radially into a mixing throat formed between two closely spaced radially extending plates or discs said throat interconnecting with said low-pressure supply duct such that a high-pressure fluid issuing from said nozzles would entrain a fluid from said low-pressure duct.

To enable the nature of the invention to be more readily understood, embodiments of the invention will now be described, solely by way of example, with reference to the accompanying drawing. In the drawing:

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagrammatic sectional view of a single-stage injector pump suitable for use as a gas pressure booster and FIG. 2 is a similar view of a two-stage injector pump.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring specifically to FIG. 1 of the drawing an injector pump comprises a central high-pressure gas supply duct 1 surrounded by a low-pressure gas duct 2 the walls of which are arranged to converge towards and form an annular duct 3 around a circumferential ring of radial gas discharge nozzles located in the end of the high-pressure supply duct 1, said nozzles discharging into an annular gap formed between two closely spaced discs or plates 5 and 6, said gap acting as a mixing throat and diffusing chamber 7 for the gases.

Disc 5 may form one wall of a circular outlet chamber 8, the disc 6 extending substantially across the diameter of said chamber but leaving an annular gas outlet space around the periphery of disc 6 such that gas may pass from the diffusing chamber towards a gas discharge outlet 9.

The high-pressure nozzles 4 are of conventional form being shaped to conform with the design criteria used for supersonic flow conditions and under operating conditions the high-pressure entraining gas is accelerated through each nozzle forming a high velocity turbulent jet such that a velocity gradient forrned at the edge of each jet causes a shearing action which draws in the surrounding relatively low-pressure fluid flowing in the low-pressure duct 2, and carries it forward into the diffusing and mixing chamber. Since the cross-sectional area of the chamber continually increases with increasing radius, the degree of diffusion is considerably enhanced.

It is desirable that the cross-sectional area of the high-pressure supply duct 1 should be a minimum of six times that of the total cross-sectional area of all the nozzle throats. It is preferable that the nozzles should be spaced equally around the duct and it is also preferable that the nozzle shall be so spaced that the distance between the adjacent edges of adjacent nozzles shall not be less than the diameter of the nozzle exit, that is, the diameters measured at the outer surface of the duct.

Additionally, the nozzles should be positioned between and equidistant the said discs and the distance between each nozzle exit and the entry to the mixing throat and diffusing chamber should preferably not be greater than 10 times the nozzle exit diameter.

The distance or gap between the two discs defining the mix-- ing throat and the diffusion chamber determines the quantity of injected fuel and the pressure lift produced at any driving or operating pressure. This distance may be varied to suit the operating conditions selected in such a way as to provide ratios between the nozzle exit area and the area of the entry 0 tothe mixing throat and diffusing chamber of area of nozzle exit/area of entry 0 to mixing throat d 0.03 to 0.3 preferably 0.05 to 0.15.

The distance between the entry a to the mixing throat and exit b from the diffusing chamber preferably should be 20 times the distance between the said discs.

It will be appreciated that the invention described permits a gas pressure booster unit to be constructed whereby the overall longitudinal dimensions are considerably reduced when compared with the previously known type of booster while the overall diameter remains substantially similar. For example a single-stage unit of 500,000 cu.ft./hour constructed in accordance with the invention would have a length of 3 I 3.5 feet.

FIG. 2 shows a two-stage gas pressure booster unit in which a high-pressure supply duct 11 is extended to feed a second stage compressor, the gases discharged from the first stage mixing throat and diffusing chamber being deflected by an inclined baffle wall 10 to an annular gas duct 13 surrounding second stage portion of tube 11. A ring of nozzles 14 located at the end of duct 11 direct high-pressure gas into the second stage mixer throat and diffusing chamber 17 formed by the annular space between two parallel discs 15 and I6 and first stage gas is entrained into the mixing throat from the duct 13. The entrained gas and the high-pressure gas are mixed and diffused as they flow radially outwards between the discs to discharge into a gas outlet chamber 18 by passing over the periphery of disc 16.

The extra length necessary to provide a second stage is approximately 1 to 1.5 fee-t and a two stage unit to provide a flow of 500,000 cu.ft./hour would be 5 feet in length. An equivalent three stage unit would be 6 feet in length.

I claim:

1. An injector pump comprising a high-pressure gas supply duct, a low-pressure gas supply duct surrounding said highpressure duct, a circumferential ring of nozzles in said highpressure duct arranged to discharge radially and divergently into a mixing throat and diffusion chamber formed between two closely spaced radially extending flat discs, said throat interconnecting with said low-pressure gas duct such that a highpressure gas issuing in discrete jets from said nozzles would entrain gas from said low-pressure duct around the periphery of each jet, one of the discs being formed as an end wall of a circular outlet chamber, the other disc extending substantially across the diameter of said chamber but leaving an annular gas outlet space around the periphery of the disc such that gas may pass from the mixing and diffusing chamber between the discs extending radially from said high-pressure duct such that first stage gas is entrained into the second stage mixing throat from the said low-pressure entry duct, the entrained gas and the high-pressure gas being mixed and diffused as they flow radially outwards between the said secondary discs to discharge into a further gas outlet chamber. 

1. An injector pump comprising a high-pressure gas supply duct, a low-pressure gas supply duct surrounding said high-pressure duct, a circumferential ring of nozzles in said high-pressure duct arranged to discharge radially and divergently into a mixing throat and diffusion chamber formed between two closely spaced radially extending flat discs, said throat interconnecting with said low-pressure gas duct such that a high-pressure gas issuing in discrete jets from said nozzles would entrain gas from said low-pressure duct around the periphery of each jet, one of the discs being formed as an end wall of a circular outlet chamber, the other disc extending substantially across the diameter of said chamber but leaving an annular gas outlet space around the periphery of the disc such that gas may pass from the mixing and diffusing chamber between the discs towards a gas discharge duct in said outlet chamber, and wherein the said discharge duct provides a low-pressure gas entry duct to the second stage of a multistage injector pump and the high-pressure duct is extended to supply a ring of second stage nozzles arranged to direct highpressure fluid into a second stage mixer throat and diffusing chamber formed by the annular space between two parallel secondary discs extending radially from said high-pressure duct such that first stage gas is entrained into the second stage mixing throat from the said low-pressure entry duct, the entrained gas and the high-pressure gas being mixed and diffused as they flow radially outwards between the said secondary discs to discharge into a further gas outlet chamber. 